NASA today enjoys the reputation of being the best in the field of lunar and planetary exploration as a result of decades of highly successful missions. But it took NASA years to earn this reputation and its earliest attempts were not always so successful. Literally just ten days after its official founding on October 1, 1958, NASA was sponsoring its very first launch of a space mission as part of a larger program which it had just inherited from the U.S. Air Force (USAF). And this was not just another attempt to launch an Earth-orbiting satellite. This was to be an attempt to send the first probe to the Moon.
During the opening months of the Space Age, the American space program was in total disarray as a wide range of civilian and military interests vied for control in the wake of the chaos resulting from the first satellite launches of the Soviet Union. In the hopes of quickly unifying the military’s research projects and securing a major share of the nation’s future space program for the Department of Defense (DoD), Secretary of Defense Neil H. McElroy established the Advanced Research Projects Agency (ARPA) on February 7, 1958. ARPA was charged with coordinating all the DoD’s advanced research, including their space projects, to help eliminate duplicate efforts among the various branches of the service. Since the entire space program at this time was connected in some way to the military, by default ARPA would be in charge of almost all aspects of the American space program until Congress and the Administration made other arrangements.
On March 27, 1958 President Eisenhower approved McElroy’s plan for ARPA to undertake its first series of space missions. The most ambitious of these was labeled “Operation Mona” which called for the launching of five probes to the Moon in hopes of beating the Soviet Union to our neighbor. Three of these attempts would be sponsored by the USAF Ballistic Missile Division while the Army Ballistic Missile Agency (ABMA) would be responsible for the last two. ARPA believed that a successful military lunar mission would not only help the US leap frog ahead of the Soviet Union in the space race but also add credibility to the military presence in space. It was felt by some that these missions could help prevent any civilian space agency that Congress might create from taking an important share of the space program from the DoD. In addition, the long-distance guidance and tracking experience gained in the project would be useful for future scientific and weapons programs.
The USAF would have the first shot at the Moon with the more ambitious of the two sets of ARPA probes under the name of “Project Able-1”. For these missions, the USAF planned to use their new Thor-Able rocket which was cobbled together from existing rocket components. The first stage of this rocket was the Thor intermediate-range ballistic missile (IRBM) which, as a weapon, had a range of 2,600 kilometers. The Thor, built by the Douglas Aircraft Company (which became McDonnell-Douglas and much later merged with Boeing) for the USAF, was about 18.6 meters long and 2.4 meters in diameter at the base. The Thor incorporated a Rocketdyne MB-3 power plant burning kerosene and liquid oxygen (LOX) to produce 668 kilonewtons of thrust.
In the Thor-Able configuration, Thor’s one-ton nuclear warhead was replaced with an adapter upon which the 1.88 metric ton upper stages were mounted. These stages were modified versions of the ones originally developed for the Navy’s Vanguard program (see “Vintage Micro: The Original Standardized Microsatellite”). The Vanguard second stage built by Douglas was modified by the builders of the USAF lunar probes, STL (Space Technology Laboratory – a division of what would become TRW), for the Thor-Able program. In the Able configuration, the second stage retained its original 0.85 meter diameter but it was shortened to 5.8 meters to optimize its size for the Thor-Able mission. The second stage’s original Aerojet General AJ10-37 liquid propellant rocket engine was replaced with the substantially improved AJ10-41 engine which generated 35 kilonewtons of thrust burning unsymmetrical dimethyl hydrazine (UDMH) and nitric acid. Before it had been selected for its lunar mission, a two-stage version of this rocket, designated Thor-Able 0, had been selected by the USAF for high-speed reentry testing of proposed ICBM reentry vehicle designs. STL had submitted the proposal for what became known as ARTV (Able Reentry Test Vehicle) on November 1, 1957 with work beginning in earnest the following month.
The third stage of what would become known as the Thor-Able 1 was the fiberglass-cased X-248 solid motor built by Allegany Ballistics Laboratory (which today is operated by ATK under contract from the US Navy). This innovative lightweight motor was an evolutionary outgrowth of work for the US Navy to develop a backup for the more conventional motor developed by the Grand Central Rocket Company for the Vanguard program. The X-248, which generated 12.5 kilonewtons of thrust for 38 seconds, was later incorporated into several other rocket designs including a high performance version of the Vanguard. All together, the Thor-Able I was 27 meters tall from its base to the top of its hemispherical “mushroom cap” payload fairing. Theoretically, the Thor-Able I could place 160 kilograms of payload into a 480-kilometer high orbit or up to 39 kilograms into a direct ascent escape trajectory to the Moon or beyond.
The USAF lunar probe, which was frequently labeled as “stage 4” in STL’s Thor-Able design, had the ambitious goal of being the first spacecraft to orbit the Moon. Under contract by the USAF, STL built three 38-kilogram spin-stabilized probes each carrying 18 kilograms of scientific instruments. By today’s standards, these would be considered microsatellites. The orbiter consisted of a wide cylindrical belt with a diameter of 74 centimeters joining two flattened fiberglass cones. At the end of the bottom cone was a ring of eight vernier solid rockets which could be fired to correct the probe’s trajectory. At the other end of the 76-centimeter tall probe was a single Thiokol TX-8 solid rocket motor that would be fired 65 hours after launch to slow the probe into lunar orbit. Without any attitude control system, the spinning probe would essentially maintain a constant orientation after its release from the launch vehicle’s final stage. Removable black and white stripes applied to the probe’s exterior before launch were used for passive thermal control to maintain the internal temperature between 16° and 29° C.
The probe’s wide belt carried the control systems, batteries, radio, and scientific instruments to measure magnetic fields, radiation, and micrometeorites. The STL probe also carried a simple camera designed and built by the Naval Ordinance Test Station (NOTS) in the hopes of obtaining the first close-up images of the Moon. This camera had a mass of only 400 grams and consisted of a small parabolic mirror that focused infrared radiation received from the Moon onto a special cell. One pixel of the image would be obtained for each revolution of the spinning probe. The scene could then be slowly built up one line at a time as the probe moved in relation to the Moon. The image scale was expected to be about 40 kilometers per pixel from a nominal range of 6,400 kilometers. The camera would be activated automatically after the camera detected the light of its target following the firing of the retrorocket. Once activated, there was sufficient battery power available to operate the camera and its dedicated 50-watt transmitter for a few hours – hopefully long enough to secure and transmit a single crude image of the Moon via the USAF’s primary tracking station in Hawaii.
Because of the mission requirements, the fixed orientation of the probe and the crude nature of the probe’s thermal control system, launches to the Moon were only possible during a four-day period each month with launch windows lasting no longer than 35 minutes. On the remote chance that the probe should accidentally impact the Moon, the spacecraft was decontaminated to minimize the chances that organisms from Earth would corrupt any future biological investigations on the Moon.
After a half year of intensive effort by the staff at STL and other USAF contractors, the first USAF lunar probe was ready for launch. On August 17, 1958 at 8:18 AM EDT, Thor 127 lifted off from Pad A at Cape Canaveral’s Launch Complex 17 (LC-17A) and into a clear Florida sky carrying the Able-1 stages and payload. For the first time in the history of our species, mankind was attempting to reach the Moon. All seemed to be going as planned as the Thor-Able accelerated towards space. But as the quickly rising rocket passed an altitude of 15 kilometers some 73.6 seconds after launch, it exploded. Transmissions from the still active Pioneer probe were received until it and the remains of the Thor-Able plummeted into the Atlantic Ocean two minutes later. The first ARPA-sponsored lunar mission had failed.
An analysis of the telemetry and hardware recovered by Navy divers showed that a fault in the turbopump in Thor’s MB-3 engine was to blame for the failure. A similar fault had also caused the failure of two earlier Thor launches including the first ARTV flight on April 24, although the Thor-Able 0 had operated satisfactorily during the two subsequent ARTV launches on July 10 and 14.
With the cause of the first Able-1 failure determined, it was decided to replace Thor 129, which had already been erected on the launch pad on August 19 in preparation for a September launch attempt, so that the fault in its MB-3 engine could be corrected. The next launch attempt was pushed back a month with a modified Thor 130 substituted to serve as the booster. In the mean time, a new name was officially adopted by the USAF for this series of flights – Pioneer. The first unsuccessful launch attempt was retroactively designated “Pioneer 0” with the next mission scheduled for October to be called “Pioneer 1”.
NASA’s First Space Mission
Before Pioneer 1 could be launch, politically motivated changes had already altered the landscape of America’s nascent space program. An act of Congress signed into law by President Eisenhower on July 29, 1958 officially established the National Aeronautics and Space Administration (NASA) to run the American civilian space program starting on October 1. Much to the chagrin of those who wanted the DoD to run the show, President Dwight Eisenhower transferred most of the DoD’s purely scientific space projects to the new agency including ARPA’s Pioneer program. With ARPA and the USAF relegated to an advisory role, the next Pioneer mission would be the first launch for the fledgling space agency.
With the USAF still officially in charge for the moment, Thor 130 was erected on the pad at LC-17A on September 22, 1958 to begin preparations for what would become the launch of NASA’s first space mission. A static test firing of the Thor without the upper stages and payload attached was successfully conducted on October 1. The second stage, with “USAF” still painted on its side, was mounted on top of the Thor the following day with the solid-propellant third stage added on October 8. The Pioneer 1 spacecraft, which finished the stack as “stage 4”, was identical to its predecessor except for the addition of an ion counter designed by Dr. James Van Allen. This new instrument was similar to those he had flown on earlier Explorer satellites launched by the ABMA team led by Wernher von Braun.
After a number of built-in and unplanned holds to attend to issues during the countdown, Thor 130 lifted off on October 11, 1958 at 4:42:13 AM EDT – only 13 seconds into its launch window. Unlike the previous attempt, the Thor first stage operated properly this time giving the Able stages their chance. The second stage fired followed by a nominal burn of the X-248 third stage. At first it seemed that the launch was a success and the probe would reach the Moon near midday on October 13.
Unfortunately, initial tracking of the receding Pioneer 1 showed that the spacecraft was travelling slower than required. In the hours following launch, continued tracking made it apparent that the probe was also off course. Analysis of the telemetry during ascent showed that the Thor autopilot had steered the rocket 2.5 degrees too high and was travelling about 244 meter per second too fast at first stage cutoff. Because of the inability of the relatively primitive second stage guidance system to adapt, the amount of loft had increased to three degrees with the second stage cutoff prematurely with ten seconds of propellant still left. This resulted in a velocity deficit of about 61 meters per second. A disturbance during separation and ignition of the third stage knocked the ascending rocket 15 degrees further north than desired. At third stage burnout, Pioneer 1 was travelling 152 meters per second shy of its intended 10,731 meter per second final velocity and 5 degrees off course. Even after firing its vernier rockets to gain another 49 meters per second, Pioneer 1 would reach no higher than 113,830 kilometers 21½ hours after launch before arcing back towards the Earth.
While reaching the Moon was out of the question, Pioneer 1 could still use its instruments to investigate this previously unexplored region of space. For the first time since their discovery earlier that year, the full extent of the Van Allen radiation belt was probed. Pioneer 1 found that it extended to 8,000 to 11,000 kilometers above the equator before fading out at an altitude of 15,000 kilometers. The Van Allen belt would not be a barrier to piloted missions passing through on their way to destinations beyond the Earth as some had begun to fear. Since Pioneer 1 travelled so much higher than any previous payload, it was also used in the first comsat tests with telemetry being relayed between tracking stations in Hawaii, Cape Canaveral and Manchester, England. It would be two months before the first dedicated comsat payload was launched as part of DoD’s Project SCORE (see “Vintage Micro: The Talking Atlas“).
To continue gathering useful data, ground controllers came up with an alternate mission plan. They decided to ignite Pioneer’s TX-8 solid retrorocket motor 28 hours after launch to raise probe’s perigee up to around 32,000 kilometers. Orbiting the Earth about once every 2½ days, Pioneer 1 could observe the outer reaches of Earth’s magnetosphere until its batteries were exhausted. It might also prove possible to use Pioneer’s camera to obtain the first image of the Earth from cislunar space.
While this plan promised to salvage something out of the flight, bad luck would strike again. The launch aim error had left Pioneer 1 spinning at an unintended angle to the Sun. The probe’s simple thermal control system could not adapt to the change and internal temperatures fell to 2° C. When the command to ignite the retrorocket was given, it failed to fire because the cold had affected the command receiver’s battery. Pioneer 1 was now forced to continue in its ballistic path which ended in a fiery reentry over the South Pacific Ocean 43 hours and 17 minutes after launch. And since the retrorocket did not fire, Pioneer’s camera failed to activate resulting in no pictures of the Earth as well. Even though Pioneer 1 did not reach the Moon, the record breaking flight still helped America’s flagging morale as preparations were made for the final launch of Project Able-1 .
In order to avoid another premature shutdown of the Thor-Able second stage on the final Able-1 flight, the guidance system was outfitted with a Doppler command system that would minimize trajectory errors and ensure a more accurate course to the Moon. On the morning of November 7, 1958 at 2:30 EST the Thor-Able carrying the 39.6 kilogram Pioneer 2 blasted off. While the first and second stages operated perfectly this time, the third stage failed to ignite thus dooming the latest NASA Moon probe. Pioneer 2 reached a peak altitude of only 1,550 kilometers before falling back to Earth 42.4 minutes after launch.
With this last attempt, NASA moved on to the next pair of missions it had inherited from ARPA’s Operation Mona: ABMA’s program to launch much smaller six-kilogram Pioneer flyby probes built by the Jet Propulsion Laboratory (JPL). While Pioneer 3 launched on December 6 only reached a peak altitude of 102,320 kilometers due to a velocity shortfall, Pioneer 4 managed to make a distant flyby of the Moon on its way into solar orbit following a successful launch on March 3, 1959 (see “Vintage Micro: The Pioneer 4 Lunar Probe”). Unfortunately, the Soviet Luna 1 probe launched on January 2 had beaten NASA’s probe to the Moon giving it yet another important space first.
Among the other ARPA lunar programs NASA inherited was another, more advanced lunar orbiter also built by STL. For these missions the Able stages were modified for use on a much larger Atlas D ICBM (see “NASA’s Forgotten Lunar Program”). The Thor-Able continued to be used by NASA for the next couple of years with mixed results although it did successfully launch the first interplanetary probe, Pioneer 5 (see “Vintage Micro: The First Interplanetary Probe”), and the first weather satellite, TIROS 1 (see “The First Weather Satellite”), before it was finally retired. Based on the experiences with the Thor-Able, Douglas significantly upgraded the various systems of the rocket to create what was initially called the Thor-Delta. Later known simply as the Delta, this rocket would become a reliable workhorse for NASA and other launch customers for decades to come.
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Here is an excellent STL-produced video from 1958 about the Pioneer 1 launch entitled Project Able-1 Space Probe: Report No. 2.
“Vintage Micro: The Pioneer 4 Lunar Probe”, Drew Ex Machina, August 2, 2014 [Post]
“NASA’s Forgotten Lunar Program”, Drew Ex Machina, September 27, 2015 [Post]
Gideon Marcus, “Pioneering Space”, Quest, Vol. 14, No. 2, pp. 52-59, 2007
Gideon Marcus, “Pioneering Space – Part II”, Quest, Vol. 14, No. 3, pp. 18-25, 2007
Adolph K. Thiel, “The Able Series of Space Probes”, May 20, 1960
“1958 NASA/USAF Space Probes (Able-1) Final Report: Volume 1 – Summary”, Space Technology Laboratory, February 18, 1959
“1958 NASA/USAF Space Probes (Able-1) Final Report: Volume 2 – Payload and Experiments”, Space Technology Laboratory, February 18, 1959